The present invention relates to a spectacle frame shape measuring apparatus for measuring the frame shape of a spectacle frame and the shape of a frame template or lens and a holder used to mount the frame template and lens on the spectacle frame shape measuring apparatus.
The shape of a frame rim (rim) of a spectacle frame when viewed from the top is generally curved along the face of a wearer. For this reason, shape measurement is performed in three dimensions by a spectacle frame shape measuring apparatus. The measurement data is therefore expressed in a cylindrical coordinate system with r (the displacement of a measurement element in the radial direction), θ (the displacement of the measurement element in the rotational direction in a horizontal plane with reference to an arbitrary point on the measurement element), and Z (the displacement of the measurement element in the height direction). For this reason, the spectacle frame shape measuring apparatus includes a horizontal driving mechanism for driving the measurement element in the radial direction, a rotational driving mechanism for rotating the measurement element in a horizontal plane, and a vertical driving mechanism for vertically driving the measurement element. In shape measurement, the measurement element is moved along the frame groove formed in the inner circumferential surface of a rim to measure the displacements r, θ, and Z. These displacement amounts are arithmetically computed to measure the shape of the rim (e.g., Japanese Utility Model Laid-Open Nos. 6-55130 and 6-55126).
FIG. 30 shows a vertical driving mechanism for a measurement element used in a conventional spectacle frame shape measuring apparatus. Note that this apparatus is of a magnetic type as a representative example. Referring to FIG. 30, reference numeral 1 denotes the rim (frame rim) of a spectacle frame; 2, a frame groove which is a groove with a V-shaped cross-section formed in the inner circumferential surface of the rim 1; 3, a measurement element; 4, a rotating table which is movable in a lateral direction and rotatable; 5, a slider disposed in the rotating table 4; and 6, a vertical driving mechanism for the measurement element 3 (a conventional apparatus having such a structure includes, for example, frame tracer GT1000 available from HOYA CORP.).
The slider 5 is coupled to a motor-driven wire (not shown) to be moved, and is biased in one direction by a constant force spring. With this arrangement, at the time of shape measurement, the measurement element 3 is pressed again the frame groove 2 of the rim 1 in the radial direction with a predetermined measurement force F (e.g., F=40 g).
The vertical driving mechanism 6 is constituted by a rod 7 having the measurement element 3 attached to the upper end, a pivot lever 8 which supports the rod 7 to be vertically movable, a linear stepping actuator 9 which pushes the pivot lever 8 upward at the time of shape measurement, and the like. The rod 7 extends through the slider 5 so as to be vertically moved and inhibited from rotating. A pin 11 is rotatably mounted in the intermediate portion of the rod 7 through a bearing 12. A linear sensor 13 for detecting the vertical movement of the rod 7 as the displacement (Z) of the measurement element 3 in the vertical direction is disposed on the lower end side of the rod 7. A specific example of this linear sensor will be described later with reference to FIGS. 30 and 31. The operation of this sensor will be described later. When no measurement is made, the rod 7 is released from the pivot lever 8 and moved to the lowermost position by its own weight, thereby evacuating the measurement element 3 to an evacuation position T which is the lowermost position.
The intermediate portion of the pivot lever 8 is axially supported by a shaft 14 so as to be pivotal in the vertical direction, and a proximal end portion 8a is biased upward by a helical extension spring 15. This provides the pivot lever 8 with a habit of pivoting counterclockwise in FIG. 30. In the normal state, a distal end portion 8b is pressed against the upper surface of a lower plate 5A of the slider 5 through a buffer member 16 made of rubber or the like so as to bear and support the pin 11 from below.
The linear stepping actuator 9 serves to push the measurement element 3 upward from the evacuation position T to a loading position Rd at the time of shape measurement, and is fixed to the lower plate 5A so as to be located immediately below the pivot lever 8. When no measurement is made, the linear stepping actuator 9 lowers a screw rod 17 to the home position (lowermost position) where it does not come into contact with the pivot lever 8. As the linear stepping actuator 9 is energized, the screw rod 17 rotates and rises to push the pivot lever 8 upward from below. As a consequence, the pivot lever 8 pivots clockwise about the shaft 14 to push the pin 11 upward. Therefore, the rod 7 is also pushed upward to move the measurement element 3 from the slider 5 to the loading position Rd indicated by the chain double-dashed lines.
The measurement unit including the slider 5 is moved to a left eye measurement position or right eye measurement position by driving of a motor (not shown). Thereafter, the measurement element 3 is moved to the loading position Rd indicated by the chain double-dashed lines by another driving motor and wire driving, and a contact portion 3A of the measurement element 3 is pressed against the groove wall of the frame groove 2. The slider 5 then holds the state wherein the contact portion 3A is pressed against the groove wall of the frame groove 2 by the constant force spring (see FIG. 12 to be described later). Subsequently, as the driving direction of the linear stepping actuator 9 changes, the screw rod 17 gradually moves downward to return to the home position. As a consequence, as the screw rod 17 moves downward, the pivot lever 8 is also pivoted and lowered by the biasing force of the helical extension spring 15 to return to the original state indicated by the solid lines in FIG. 30.
On the other hand, the contact portion 3A of the measurement element 3 is pressed against the frame groove 2 by the constant force spring with the predetermined measurement force F, and hence the measurement element 3 does not fall even without the support of the pivot lever 8. When the rotating table 4 is rotated in this state, the contact portion 3A of the measurement element 3 moves along the frame groove 2 to perform shape measurement (r, θ, Z) of the rim 1.
In measuring the shape of the frame groove 2, as the rotating table 4 rotates, the slider 5 moves in a lateral direction, and the contact portion 3A of the measurement element 3 vertically moves along the frame groove 2, thereby detecting the displacement (r) of the slider 5 on the rotating table 4 in a lateral direction, the rotational angle θ of the slider 5, and the displacement Z of the rod 7 in the vertical direction. With this operation, the shape of the rim is three-dimensionally measured. The rotational angle (θ) of the rotating table 4 can be measured by a control method for a pulse motor (stepping motor) or the like without preparing any detection means.
When a rim shape is to be measured, a measurement element having a shape conforming to the rim groove of the frame must be used. For this reason, conventionally, for example, a feeler in the form of an abacus counter is used as a measurement element. The angle of the vertex portion of this feeler is set to be equal to the groove angle (120° according to the industry standard) of the bevel grinding wheel of a lens edger (for example, Japanese Patent Publication No. 1-23721).
In the frame shape measuring apparatus disclosed in Japanese Patent Publication No. 1-23721, the shape of the measurement element is made to almost conform to the shape of the bevel grinding wheel as a lens cutting tool. This eliminates the necessity to correct working with respect to measurement data.
When the shape measurement is completed, the actuator 9 is driven to raise the screw rod 17 to make the screw rod 17 push the pivot lever 8 upward to the height position of the pin 11. The slider 5 then moves backward to evacuate the contact portion 3A of the measurement element 3 from the frame groove 2.
When the contact portion 3A of the measurement element 3 evacuates from the frame groove 2, since the rod 7 itself tries to move downward due to its own weight, the pivot lever 8 bears and supports the bearing 12. As the driving direction of the actuator 9 changes afterward, the screw rod 17 moves downward to make the pivot lever 8 gradually pivot and move downward to return to the home position. For this reason, the rod 7 also gradually moves downward together with the pivot lever 8, thus preventing the rod 7 from abruptly falling.
The above rim shape measurement using the measurement element is sequentially performed for the left and right rims (see, for example, Japanese Utility Model Laid-Open No. 6-55128).
The spectacle frame holder disclosed in Japanese Utility Model Laid-Open No. 6-55128 which holds a spectacle frame can freely move in a lateral direction. By moving this apparatus to the left or right, measurement for the right rim and measurement for the left rim are switched. When such rim measurement operations are to be switched, the measurement element is temporarily evacuated below by a driving unit to prevent the rim from coming into contact with the measurement element.
As a Z-axis measuring unit for measuring the displacement Z in the height direction, in particular, in measuring the shape of a rim by using the above measurement element, an optical measuring unit (see, for example, Japanese Patent Laid-Open No. 1-305308) or a magnetic measuring unit is used.
As shown in FIG. 31, an optical Z-axis measuring unit A is designed such that a charge-coupled device (CCD) line image sensor B and a light-emitting diode C serving as a light source are arranged to oppose each other through the lower end portion of a measurement element D. As the measurement element D moves vertically, the boundary between the shadow of the measurement element D and a bright portion which is formed on the CCD line image sensor B moves vertically. Therefore, by detecting the distance from an end of the measurement surface of the CCD line image sensor B to this boundary, a displacement Z of the measurement element D in the vertical direction can be measured.
Rimless spectacles are designed such that lenses are held by suspending their lower portions with nylon threads or lenses called a two-point frame or three-piece frame are held with screws extending through screw holes formed in the lenses. In this case, since no frame shape can be measured, a frame temperate in the form of a flat plate is prepared, and the shape of the frame temperate is measured. When processed lenses are edged to be reduced in size and mounted in a spectacle frame having a suitable size, shape measurement is performed for the lenses themselves. For this reason, a spectacle frame shape measuring apparatus of this type has a holder as an attachment. When a frame template or lens is to be measured, the frame template or lens is fixed on the holder, and the holder is mounted on the apparatus.
As a holder used in a spectacle frame shape measuring apparatus, a template holder is known (see, for example, Japanese Patent Laid-Open No. 2000-317795). This template holder has the following components in its main body: a template holding portion having a movable shaft which is a shaft to be engaged with a central hole formed in a template (frame template) and can move in the radial direction of the template, an elastic member which biases the movable shaft in the radial direction of the template, and a push member for returning the movable shaft in a direction opposite to the biasing direction of the elastic member. The template holder body also incorporates a dummy lens holding portion having a movable member for pressing the base of a cup to which a dummy lens is fixed. The above elastic member presses the movable member against the base of the cup. One surface of the template holder body is used as a template holding portion, and the reverse surface to this one surface is used as a dummy lens holding portion. Using the template body while turning it over makes it possible to perform shape measurement for a template and dummy lens by using the single holder.
The above spectacle frame shape measuring apparatus, however, involves various problems as described below.
First of all, since the measurement element 3, rod 7, pin 11, bearing 12, and the like constitute the movable member 18 which moves vertically at the time of shape measurement for the rim 1, it is preferable that the displacement Z of the measurement element 3 in the vertical direction be measured after the weight of the movable member 18 is minimized so as not to apply a load on the frame groove 2.
In the conventional vertical driving mechanism 6 described above, however, since the contact portion 3A of the measurement element 3 is pressed against the groove wall of the frame groove 2 with the measurement force F by the constant force spring which biases the slider 5 in one direction so as to engage the measurement element 3 with the frame groove 2, the overall weight of the movable member 18 is applied as a load onto the frame groove 2, and the frictional force between the frame groove 2 and contact portion 3A is increased by this load and the measurement force F. For this reason, if, for example, the contact portion 3A of the measurement element 3 cannot be smoothly moved along the frame groove 2 due to changes in parts over time and the like, the contact portion comes off the frame groove 2. As a consequence, the displacement Z in the vertical direction cannot be accurately measured.
If the spring force of the constant force spring is reduced to decrease the measurement force F so as to improve the follow-up characteristics of the contact portion 3A with respect to the frame groove 2, the contact portion 3A easily comes off the frame groove 2.
According to the frame shape measuring apparatus disclosed in Japanese Patent Publication No. 1-23721 described above, the feeler in the form of an abacus counter tends to come off a thin frame groove, and it is difficult to smoothly control the rotation of the feeler. In addition, if the opening angle of a frame groove changes, the contact position between the feeler in the form of an abacus counter and the frame groove changes, resulting in a measurement error in the displacement r in the radial direction. More specifically, as shown in FIG. 32A, the frame groove 2 of the rim 1 of the spectacle frame is generally formed into a V-shaped groove with an opening angle α of 110°. However, depending on spectacle frames, frame grooves have α=100° and 90°, as shown in FIGS. 32B and 32C. If, therefore, rim shapes are measured by using the measurement element 3 having a vertex portion with an angle β of 120°, a distance W between the groove bottom and the measurement element 3 varies depending on the opening angle α of the frame groove 2. The distance W increases as the opening angle α decreases.
This distance W becomes a measurement error in the displacement r in the radial direction. For this reason, in order to obtain true frame shape data, actually measured values must be corrected by adding different correction values thereto for the respective types of frame grooves 2 (for example, with opening angles α of 110°, 100°, and 90°).
In addition, since a unit or attachment for measuring the opening angle α of the frame groove 2 is required, the manufacturing cost of the measuring apparatus itself increases.
In the case of a measurement element 3M having a hemispherical contact portion, as shown in FIG. 33, contact point P1 and P2 can be moved to the deeper side of the frame groove 2 than the contact points q1 and q2 of the measurement element 3 in the form of an abacus counter with the frame groove 2, and hence the measurement element 3M does not easily come off the frame groove 2 even with an abrupt change in the displacement Z in the height direction of the frame groove 2.
However, as a diameter D of a contact portion 3MA of a measurement element 4 increases, the contact points P1 and P2 move away from the groove bottom of the frame groove 2 as in the case of the measurement element 3 in the form of an abacus counter. As a consequence, the measurement element 3M tends to come off the frame groove 2 during measurement.
In the conventional spectacle frame shape measuring apparatus described above, when shape measurement for the frame groove 2 is completed, and the measurement element 3 is temporarily evacuated to the evacuation position T at a lower position, the actuator 9 is driven to raise the screw rod 17 to push the pivot level 8, thereby supporting the pin 11 from below. The actuator 9 is then driven in the reverse direction to lower the screw rod 17 to gradually lower the rod 7 together with the pivot level 8, thereby preventing the rod 7 from abruptly falling.
However, because of the structure in which the movable member constituted by the measurement element 3, rod 7, pin 11, bearing 12, and the like is lowered by its own weight to evacuate the measurement element 3 to the evacuation position T, if the movable member is snagged in the process of movement due the friction between the slider 5 and the rod 7 or the like, the measurement element 3 cannot be evacuated to the evacuation position T.
Consider further the Z-axis measuring unit. The conventional Z-axis measuring unit A shown in FIG. 31 uses the lower end portion of the measurement element D as a component of the measuring unit. For this reason, the measurement element D must be elongated by the length measured by the Z-axis measuring unit A. As a consequence, the lower end portion of the measurement element D extends below a slide plate E to increase the height of the spectacle frame shape measuring apparatus itself, resulting in hindering the formation of a compact structure.
In a conventional Z-axis measuring unit 13 shown in FIG. 30, as in the Z-axis measuring unit A, a sensor rod 13B integrally extends from the lower end of the rod 7, and hence the total length of the rod 7 increases, resulting in difficulty in decreasing the height of the spectacle frame shape measuring apparatus.
As described above, shape measurement for spectacles of a type using no frame rim is performed by using a frame template and template holder.
A conventional holder uses a screw as a pushing member, and a template is attached to or detached from the template holder by rotating the pushing member so as to move a movable shaft forward or backward. If, therefore, the pushing member moves a long distance, the pushing member must be rotated many times. Therefore, the template cannot be attached or detached at one touch, and it takes much time for attachment/detachment, resulting in poor handling.
In addition, since the elastic member biases the movable shaft through the movable member, when a dummy lens is to be attached or detached, the movable shaft and movable member must be moved against the elastic member by rotating the pushing member. For this reason, the dummy lens cannot be attached or detached at one touch either; a long period of time is required for attachment or detachment.
The above conventional spectacle frame shape measuring apparatus has three measurement modes, i.e., a spectacle frame measurement mode, frame template measurement mode, and lens measurement mode. In addition, a spectacle frame has left and right rims, left and right frame templates, and left and right lenses. Therefore, in each measurement mode, whether measurement is to be done on the left side or right side must be designated.
Conventionally, therefore, when measurement is to be done, the operator operates a button provided on a control panel to designate one of the spectacle frame measurement mode, frame template measurement mode, and lens measurement mode, and to also designate whether to perform measurement on the left side or right side.
Making two designations, i.e., designation of a measurement mode and designation of measurement on the left side or right side, in this manner imposes a heavy mental burden on the operator. This may cause a designation error.